Photoconductive composition and element employing a sensitizer and a light filtering substance

ABSTRACT

A photoconductive material comprises a photoconductor, a sensitizer and a light filtering substance such as a dye or pigment which itself displays substantially no sensitizing action, but is capable of absorbing light of an undesired wave length, whereby the wave length region to which the photoconductor is sensitive is controlled by filter effect of the light filtering substance so that the photoconductor is rendered sensitive only to light of a specific wave length region.

'United States Patent Mori et a1.

[ Oct. 28, 1975 PHOTOCONDUCTIVE COMPOSITION AND ELEMENT EMPLOYING A SENSITIZER AND A LIGHT FILTERING SUBSTANCE Inventors: Yaski Mori; Hirosada. Morishita;

Nobuhiko Shito, all of Hitachi, Japan Assignee: Hitachi, Ltd., Japan Filed: July 25, 1973 Appl. No.: 382,338

Foreign Application Priority Data Aug. 7, 1972 Japan 47-78388 U.S. Cl. 96/l.7; 96/1.2; 96/1.6 Int. Cl. l. G03G 5/12; G036 5/09 Field of Search 96/1.2, 1.6, 1.7

References Cited UNITED STATES PATENTS Johnson et a1 96/l.2

Land 96/1.2 X

Miller et al. 96/1.2

Takumoto 96/l.2 X

3,329,590 7/1967 Renfrew 96/l.2 X 3,556,783 171971 Kyriakakis 96/l.2 3,630,729 12/1971 Bach et a1 l 96/1.2 3,672,887 6/1972 Matsumoto et a1... 96/1.2 3,748,125 7/1973 l-lercock et al. 96/l.2

FOREIGN PATENTS OR APPLICATIONS 994,679 6/1965 United Kingdom 96/1.2

1,071,433 6/1967 United Kingdom 96/1.2

Primary ExaminerRoland E. Martin, Jr. Assistant Examiner.lohn R. Miller Attorney, Agent, or FirmCraig & Antonelli [57] ABSTRACT A photoconductive material comprises a photoconductor, a sensitizer and a light filtering substance such as a dye or pigment which itself displays substantially no sensitizing action, but is capable of absorbing light of an undesired wave length, whereby the wave length region to which the photoconductor is sensitive is controlled by filter effect of the light filtering substance so that the photoconductor is rendered sensitive only to light of a specific wave length region.

15 Claims, 12 Drawing Figures US. Patent Oct. 28 1975 F l G.

sheet 1 on 3,915,703

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F l G. 2

[I l A I 400 soo 600 700 F I G. 4

F I G. 6

F I G. 5

F I G. 7

A l J 400 500 600 700 US. Patent Oct. 28, 1975 Sheet 2 of2 3,915,703

& Fl. 9 (GREEN) l I l A I 400 500 so 70 FlG. :0

(RED) FIGII BLUE PHOTOCONDUCTIVE COMPOSITION AND ELEMENT EMPLOYING A SENSITIZER AND A LIGHT FILTERING SUBSTANCE Electrophotography is usually accomplished by charging a photoconductor layer formed on an electroconductive support in a high electric field and then exposing the layer to a pattern of light through an original. Those portions of the photoconductor layer which are exposed to the light becomes electroconductive, whereby the charge is earthed and leaks away. Images are usually obtained by developing the latent image by allowing toners to stick to those portions of the photoconductor layer in which the charge remains. A color image can be obtained by forming said photoconductor layer with three kinds of mosaics which are respectively sensitive to spectra of three regions of red, green and blue light.

It is known that when the surface of insensitized photoconductor layer is coated with a sensitizing dye, the layer itself becomes photoconductive to light absorbed by the sensitizing dye. Utilizing said characteristics, mosaics which are sensitive to spectra of different regions can be produced by coating different dyes to insensitized photoconductor layer by silk screen in such a manner that the different dyes do not overlap each other. Alternatively, mosaics which are respectively sensitive to spectra of different regions can be produced by charging insensitized photoconductor layer, exposing the layer through a mosaic screen pattern and developing the latent image with a developer comprising a sensitizing dye.

As mentioned above, in the color electrophotographic method where the photoconductor layer itself has selective sensitivity to spectra in the wave length region to which the photoconductor has sensitivity increased by sensitizing dye is controlled in order to reproduce color close to that of original. Therefore, even such dyes as having excellent sensitizing efficiency cannot be used when the wave length region to which the photoconductor has sensitivity is wider or narrower than desired or is biased or shifted. Especially, in the dye-transfer type photoconductor layer (according to said type, after an image is formed, the dye is transferred to another recording material) containing a large amount of a dye, the spectrum absorbed by the dye is apt to become wider and simultaneously the wave length region to which the photoconductor is sensitive also becomes wider. Moreover, since maximum wave length to which the photoconductor is sensitive also shifts, the wave length region slips from the purpose and as the result, it is impossible to reproduce color close to that of an original.

An object of the present invention is to provide a photoconductive material for color electrophotography for obtaining a color image having color close to that of original.

Further object of the present invention is to provide a photoconductive material for electrophotography having selective photosensitivity to spectra of specific regions without causing reduction of sensitizing action of sensitizer.

More specifically, the object of the present invention is to provide photoconductive material for electrophotography which have selective photosensitivity to spectra of three basic lights, namely, red, green and blue, respectively.

Still further object of the present invention is to provide three kinds of photoconductive materials for color electrophotography which comprise a photoconductive material sensitive only to the spectra of red, a photoconductive material sensitive only to the spectrum of green and a photoconductive material sensitive only to the specturm of blue lights. Other objects will become apparent from the following explanation, taken in conjunction with the accompanying drawings.

FIG. 1 is the cross-sectional view of a recording medium for electrophotography of the present invention. FIGS. 2, 4 and 6 are spectrograms of the conventional photoconductors for green, red and blue lights. FIGS. 3, 5 and 7 are spectrograms of the photoconductor of the present invention and correspond to FIGS. 2, 4 and 6, respectively. FIG. 8 shows a rough sketch of an optical system of color reproduction. FIGS. 9, l0 and 11 are spectrograms of photoconductor obtained in Example l0 hereinafter mentioned. FIG. 12 is a rough sketch of the photoconductor in mosaic pattern in which 1 l is an insulating support, 12 is a photoconductive layer and 13 is mosaics and C means cyan, M means magenta and Y means yellow.

The present invention provides a photoconductive material for color electrophography which has selective sensitivity to spectra of three basic lights of red, green and blue, respectively by controlling wave length region to which the photoconductor layer on electroconductive layer is sensitive. That is, according to the present invention, a sensitizer and a light filtering substance selected from the group of dyes and pigments are added to the photoconductor layer so that there is provided a photoconductive material for color electrophotography utilizing the filter effect obtained by light filtering effect of the specific dye or pigment.

The wave length region to which the photoconductive material of the present invention is sensitive is controlled depending upon the kind of the light filtering substance and thus the photoconductive material has sensitivities to spectra of specific regions. This is because the photosensitivity of the photoconductor significantly decreases at about the maximum light absorption wave length of the dye or pigment added as the light filtering substance and no effect is given at the wave lengths which are not absorbed in a large amount by the dye or pigment. That is, the dyes and pigments display the same effect as filter does. The filter effect of the dyes and pigments is considered to be exhibited due to the following reason. That is, the sensitizer contained in the photoconductor layer absorbs the light of the specific wave length to transmit the energy to the photoconductor, which is then excited thereby to exhibit conductivity. In this case, when the dye or pigment having substantially no sensitizing action but having only absorption of the light is added to the photoconductor, such the dye or pigment does not transmit the energy to the photoconductor. As the result, sensitivity of the photoconductive material with respect to the light absorbed by the dye or pigment will markedly decrease. The present invention skilfully utilizes such filter effect of the dye and pigment to control region of wave length to which the photoconductive material is sensitive and to make the photoconductive material sensitiveto the spectra of specific wave length regions. The amount of light absorbed by the light filtering substance is preferably 10 times the amount of light absorbed by the sensitizer. Therefore, the larger the amount of the light filtering substance is, the higher the effect is. However, when the amount is too large, the wave length region to which the photoconductive material is sensitive is unnecessarily limited and, in addition thereto the photoconductor itself becomes brittle. Therefore, too much addition of the dye and pigment is not desired.

The photoconductive material for electrophotography according to the present invention may be applied as a photoconductive layer 3 on support 1 through conductive layer 2 to form a recording medium as shown in FIG. 1. In FIG. 1, support 1 may also serve as electroconductive layer 2 by imparting electroconductivity to the support.

As the photoconductor, known inorganic photoconductive materials such as selenium, zinc oxide, titanium oxide, cadmium sulfide, etc. can be used. Furthermore, organic photoconductors such as aromatic or heterocyclic vinyl polymers including poly-N vinyl carbazole, polyvinylanthracene, poly-9-(p-vinylphenyl) anthracene, poly-9-anthroic acid vinyl ester can also be used.

Regarding the sensitizier, the known sensitizers may be used, e.g., Patent blue (C.I. 42015), Victoria blue (C.I. 44045), Nile blue (C.I. 51180), methylene blue (C.I. 52015), Erioglaucine (C.I. 42045), etc. may be used as red color sensitizer; Pyronine B (C.I. 45010), Phloxine B (C.I. 45410), Methylene Violet (C.I. 50205), Rhodamine B (C.I. 45440), Rhodamine 6G (C.I. 45160), etc. may be used as green color sensitizer; and 3-carboxymethyl-5-3-ethyl-2(3)- benzothiazolylidene rhodamine-triethylamine salt, auramine (C.I. 41000), Setoflavine T (C.I. 49005), Acridine Yellow (C.I. 46025), etc. may be used as blue color sensitizer. One or more of these sensitizers depending on the spectra are added to the photoconductor in an amount of 0003- parts by weight per 100 parts by weight of the photoconductor to attain sensitization.

The light filtering substance selected from the group of dyes and pigments which are added for controlling the wave length region to which the photoconductor has sensitivity must show effective light absorbing action in such an amount as giving no adverse effects on the photoconductor layer. It should be noted, however, that some dyes have high sensitizing action and these cannot be used as the light filtering substance in the present invention. Therefore the dyes for controlling the wave length region are those which have substantially no sensitizing action to the photoconductor. Examples of these pigments which satisfy the above requirements are as follows:

Hansa Yellow G (Cl-11680), Benzidine Yellow GR (Cl-21090), Permanent Yellow (Cl-20040), Ind. Yellow G (CI-70600), Permanent Red GG (CI-12075), Pyrazolone Orange (Cl-21110), Vulcan Orange (CI- 21160), Ind. Brill. Orange GR (Cl-71105), Para Red (Cl-12070), Permanent Red FRR (Cl-12310), Toluidine Red (Cl-12120), Permanent Red R (Cl-12085), Permanent Carmine FB (Cl-12490), Permanent Red F4R (Cl-12335), Permanent Bordo FRR (Cl-12385), Brillant Fast Scarlet (Cl-12315), Pyrazolone Red B (CI-21120), Bordo 5B (CI-12170), Watchung Red (Cl-15865), Lithol Red (CI-15630), Lake Red C (CI- 15585), Brilliant Carmine 6B (Cl-15850), Rhodamine 6G Lake (CI-45160), Rhodamine B Lake (Cl-45170), Victria Blue Lake (Cl-44045), Phthalocyanine Blue B (Cl-74160), Cu-Phthalocyanine (Cl-74160), Fast Sky Blue (Cl-74200), Diamond Green Lake (CI-42040), Pigment Green B (Cl-10006), Phthalocyanine Green (CI-74260) Examples of the dyes which satisfy the above require- 5 ments are as follows:

Direct colors such as Quinoline Yellow P (CI- 47035), Direct Fast Yellow A (Cl- 300), Direct Fast Yellow A (CI-40000), Primuline (CI-49000), Benzo Orange RS (Cl-22920), Direct Orange GG (CI- 23375), Direct Orange R (Cl-22130), Direct Coupling Orange (CI-23370), Sirius Supra Orange 3R (CI- 40265), Direct Bordeaux B (CI-22150), Congo Red (Cl-22120), Direct Violet N (Cl-22570), Sirius Supra Violet BL (Cl-29125), Benzo Blue BS (CI-23710), Sirius Supra Blue F3R (Cl-27925), Sirius Blue 6G (CI- 34230), Benzo Viscose Blue RL (CI-23150), Direct Green G (Cl-30315);

Acids colors such as Acid Fast Red B (Cl-14680), Chrome Red BG (Cl-27200), Acid Blue B (Cl-50315), Cyananthrol R (CI-62085), Fast Navy Blue (CI- 13390), Acid Cyanine 5R (CI-26400), Wool Fast Green B (CI-2044), Acid Orange (CI-15510), Cytonine Y (Cl-13090), Sunset Yellow (Cl-15985), Acid Brown G (CI-20170);

Mordant colors such as Chrome Yellow G (Cl-14010) Chrome Red B (Cl18760) Alizarine Blue S (CI-67415) Chrome Violet B (Cl-17290) Chrome Green F (Cl-17225);

Sulphur colors such as Sulphur Orange (Cl-53105) Sulphur Blue V (Cl-53235) Sulphur Blue RC (Cl-53440) Sulphur Brown G (CI-53020); Vat colors such as Threne Red (CI-67000) Threne Olive (Cl-69525) 3 5 Threne Orange RRTS (Cl-59705) Threne Marine Blue R (CI-70500); and Oil colors such as Oil Blue G (CI-61525) Oil Brown BB (Cl-12020),

etc

Among the above dyes and pigments, yellowish and orange ones are used for filtering the light having smaller wave lengths than green light. Green, blue and violet ones are used for filtering the light having larger wave length than green light. When a photoconductive material contains the sensitizer for green light and the above two kinds of the light filtering substances, it can become sensitive substantially only to green light.

In case of a photoconductive material containing a sensitizer for red color, red dyes or pigments listed above are added in order to filter the light having the smaller wave length than red light, so that the photoconductive material becomes sensitive only to red light.

Similarly, in case of a photoconductive material containing a sensitizer for blue light, orange dyes or pigments listed above are added in order to filter the light having the larger wave length than blue light, so that the photoconductive material becomes sensitive substantially only to blue light.

The rough classification of red, green and blue lights in the present invention is made by the wave length of the lights. That is, red light has a wave length larger than 600 mu; green light has a wave length of 500 to 590 mu; and blue light has a wave length smaller than 500 mp..

The amount of at least one of said pigments and dyes is preferably 5-30 parts by weight per 100 parts by weight of the photoconductor. Although the amount is EXAMPLE 1 A mixture having the following compositions was prepared in a ball mill.

Photoconductive zinc oxide (produced by Tokyo Seiren K.K.) Silicone resin (KR 214 produced by Shinetsu Chemical Co., Ltd.) Toluene 100 parts by weight 100 parts by weight 80 parts by weight Five parts of 0.2 solution of Pyronine B (CI. 45010) in methanol was added dropwise to said mixture while stirring to adsorb it to the photoconductor. Then, I parts of Pyronine B was further added and a mixture was again prepared ina ball mill.

Thus obtained mixture was coated on a coat paper subjected to electronconductive treatment so that thickness of the film after dried was 10 ,u.. After drying, the film was charged by corona discharge at kV and exposed by a spectrograph. Then, thus exposed film was developed with a liquid toner (Copyster prepared by Mita Kogyo K.K.) to obtain spectrogram as shown in FIG. 2. As is clear from this diagrams the wave length region to which the photoconductor was sensitive was in 440-590 mp. In order to produce a photoconductor which is selectively sensitive to green light for color electrophotography, the sensitive region of less than 500 mp. is not necessary and said photoconductor was sensitive to blue light, too.

For removing said defect, to said mixture to which parts of Pyronine B was added 5 parts of Pyrazolone Orange (CI. 21110) which has maximum absorption of spectrum of 470 mp A photoconductive material was produced from thus obtained mixture in the same manner as mentioned above. The resultant spectrogram is shown in FIG. 3. As is clear from the diagram, the photoconductor was selectively sensitive only to green light, namely, the sensitive wave length region (referred to as sensitive region hereinafter) to which the photoconductor was sensitive was changed from 440-590 my. to 500-590 mp..

A recording medium shown in FIG. 1 was prepared and was negatively charged at 6 kV. Then, this was exposed through a color original containing network by a photographic enlarger at F 5.6 from a light source of I50 W tungsten lamp from a height of 30 cm for 3 seconds. Thereafter, the exposed recording medium was developed with a reversal toner (N-P toner produced by Konishiroku K.K.) and fixed by heating it at 80C for about 3 seconds to obtain a negative toner image.

A gelatin coated paper was immersed in a mixed liquid of 30 parts of ethanol and 1 part of dimethylformamide and immediately withdrawn from the liquid. The negative toner image was pressed onto the paper to cause transfer of Pyronine B to obtain an excellent positive magneta image. The Pyrazolone Orange did not dissolve out into the solvent which was used for transfer and the image showed a good light absorption characteristic as magenta color.

EXAMPLE 2 In this Example, a photosensitive material sensitive to cyan color was prepared using Watchung Red.

A photoconductive material having the following composition was prepared in the same manner as in Example l.

Photoconductive zinc oxide 100 parts Silicone resin (KR 214 produced by Shinetsu Chemical Co., Ltd.) 100 parts Erioglaucine (CI. 42045) 10 parts Toluene parts Dimethylformamide 10 parts Watchung Red (C.I. 15865) 12 parts Thus, a spectrogram as shown in FIG. 5 was obtained with respect to a recording medium prepared by using the above photoconductive material. A spectrogram in case of containing no Watchung Red is shown in FIG. 4. As is clear from these diagrams, when Watchung Red was not contained, the photoconductor had the sensitive region to the light of 500 -680 III/J. while addition of Watchung Red resulted in shift of the sensitive region to 600-700 mg.

EXAMPLE 3 In this Example, a photoconductive material sensitive to yellow color was prepared.

The procedure of Example 2 was repeated except that Erioglaucine was replaced by Auramine (CI. 41000) and Watchung Red was replaced by Phthalocyanine Blue (CI. 74160). The spectrograms in case of containing no phthalocyanine Blue and in case of containing it are shown in FIGS. 6 and 7, respectively. As is clear from comparison of these diagrams, the sensitive region to 400-530 mp. was shifted to 400-500 mu.

EXAMPLE 4 The recording papers utilizing the photoconductive materials of the present invention sensitive to cyan, magenta and yellow colors which were each prepared in Examples 1, 2 and 3 were separately charged and were respectively and simultaneously exposed through a color original which was equally divided into three parts by a simple optical system comprising two half mirrors 4 and 5 and one mirror 6 as shown in FIG. 8. Thus exposed papers were simultaneously subjected to reversal development and fixation and thereafter the images were transferred to one transfer paper. In this case, solvent was applied to the recording paper. The obtained color images were clear and color reproduction was excellent. Since only the dye was transferred to the transferring paper and pigment was not contained, these recording papers were especially advantageous for color reproduction of mixed color portion.

In the same manner as mentioned above, color images were prepared from three recording papers which was sensitive to cyan, magenta and yellow colors, but did not contain the dyes of the present invention capable of controlling the wave length region. Thus prepared images were not good in reproduction of blue color and were not so clear as a whole as compared with those obtained using the dyes as the light filtering substance.

EXAMPLE A photoconductive material was prepared in accordance with the same manner as in Example 1 except that Quinoline Yellow (C.l. 47035) was substituted for Pyrazolone Orange. This photoconductive material was sensitive to spectrum of 490-590 mu.

EXAMPLE 6 A photoconductive material was prepared in the same manner as Example 1 except that 5 parts of Pyrazolone Orange was replaced with Sirius Supra Orange (C.l. 40235). This photoconductive material was sensitive to spectrum of 500-590 mu.

EXAMPLE 7 A photoconductive material was prepared in the same manner as in Example 1 except that 5 parts of Pyrazolone Orange was replaced with 4 parts of Sulphur Orange (C.l. 53105). The resultant photoconductive material layer was sensitive to a spectrum of 495 590 EXAMPLE 8 Polyvinyl carbazol 100 parts 0.5 7: Ethanolic solution of Crystal Violet (C.l. 42555) 2 parts Toluene 1.000 parts The above components were agitated until a homogeneous solution was obtained. To the resultant solution was added dropwise 5 parts of 1 ethanolic solution of Congo Red (C.l. 22120) and they were agitated until a homogeneous solution was obtained. The resultant solution was coated on an aluminum plate by an applicator so that thickness of film was 5 p" The resultant photoconductive material was sensitive to a spectrum of 600-700 mp.

The photoconductive materials prepared in the above Examples 5-8 could be used for the conventional dry powder transfer process.

EXAMPLE 9 The photoconductive materials having the compositions as in Examples 1, 2 and 3 which contained the pigments as the light filtering substance were printed three times in the order of cyan, magenta and yellow sensitive compositions in mosaic pattern of an intersecting angle of 60 and of 50 lines/inch by means of relief printing so that the compositions did not overlap with each other. The printed matter was charged, color-exposed, subjected to reversal toner development and fixed. Thereafter, the image was transferred to a transferring material to obtain a good color image. This process comprises one time exposure, one time development and one time transfer and hence this is very simple and easy process.

EXAMPLE 10 A mixture comprising the following components and sensitive to the whole region of white light was prepared.

Photoconductive zinc oxide 100 parts Silicone resin (KR 214 produced -Continued 100 parts 40 parts To the mixture were added dropwise 5 parts of 2 methanolic solution of Bromophenol Blue and 5 parts of 2 solution of dimethylamino benzylidene rhodanine in methylcellosolve while stirring. Three batches of this mixture were prepared, to which 5 parts of Malachite Green (C.l. 42000) and 3 parts of Acid Yellow 23, (C.l. 19140); 5 parts of Acid Red 80 (C.l. 68215); and 5 parts of Acid Blue 45 (C.l. 63010) were added, respectively and each of these three mixtures was further agitated for 4 to 5 hours.

Thus, three mixtures colored in green, red and blue were obtained. Recording papers were produced using each of these three mixtures in the same manner as in Example 1. Spectrogram of each paper are shown in FIGS. 9, 10 and 11.

In the same manner as in Example 9, said photoconductive compositions were printed by the relief printing in mosaic pattern of the three colors to obtain one photosensitive plate. After charging the plate, this was exposed through a color image and developed with Xerox 914 toner (produced by Xerox Co., Ltd) and then fixed. A polyethylene terephthalate film having a thickness of 200p. on which gelatin was coated in a thickness of 3 1. onto said fixed mosaic plate for 30-60 seconds and the gelatin layer was sufficiently swelled with dimethylformamide, and then the film was gently removed. Color of the mosaic was transferred to the portion to which no toner sticked and the portion to which toner sticked was colored in bluish black due to the dye contained in the toner. This film to which color was transferred was observed with transmission light to find that a good color image was obtained. In this case, when a positive original of 36 mm in size was enlarged to B5 size or more and reproduced, discontinuity of mosaics was not conspicuous and good impression was given. However, somewhat dark impression was given as a whole and it was necessary to employ a strong light source for transmission.

What is claimed is:

1. A photoconductive mixture sensitive to light of a limited region of the spectrum comprising a photoconductor, at least one sensitizer dye sensitive to light in a broader region of the spectrum than said limited region, said broader region including said limited region, and at least one dyestuff or pigment absorbing light in said broader region except for light in said limited region whereby undesired sensitizing of said photoconductor by light outside said limited region is prevented, said mixture containing 5 to 30 parts by weight of said at least one dyestuff or pigment and 0.003 to 10 parts by weight of said at least one sensitizer dye based on 100 parts by weight of said photoconductor.

2. A photoconductive material according to claim 1, wherein said sensitizer absorbs mainly green light and said light filtering substance is capable of absorbing light other than said green light.

3. A photoconductive material according to claim 2, wherein said mixture contains yellowish or orange dyestuff or pigment for filtering light having smaller wave lengths than green light and a green, blue or violet dye or pigment for filtering light having larger wave lengths than green light.

4. A photoconductive material according to claim 1, wherein said sensitizer absorbs mainly red light and said light filtering substance is capable of absorbing light other than said red light.

5. The photoconductive material of claim 4, wherein said mixture contains a red dye or pigment for filtering light having smaller wave lengths than red light.

6. A photoconductive material according to claim 1, wherein said sensitizer absorbs mainly blue light and said light filtering substance is capable of absorbing light other than said blue light.

7. A photoconductive material according to claim 6, wherein said mixture contains an orange dye or pigment for filtering light having larger wave lengths than blue light.

8. A photoconductive material according to claim 1, wherein the photoconductor is selected from the group consisting of selenium, zinc oxide, titanium oxide and cadmium sulfide.

9. A photoconductive material according to claim 1, wherein the photoconductor is an organic polymer selected from the group consisting of an aromatic and heterocyclic vinyl polymers.

10. A photoconductive element comprising three kinds of homogeneous mixtures, each being regularly arranged in mosaic pattern on an electroconductive support, said homogeneous mixtures including the following three photoconductive compositions:

1. a first photoconductive composition comprising a photoconductor sensitive to the visible light; a sensitizing amount of a sensitizer capable of absorbing green light for enhancing sensitivity of said first photoconductive composition with respect to said green light; and a light filtering substance insensitive to said visible light and capable of absorbing light other than the green light, whereby said first photoconductive composition is rendered sensitive only to said green light;

2. a second photoconductive composition comprising a photoconductor sensitive to the visible light; a sensitizing amount of a sensitizer capable of absorbing red light for enhancing sensitivity of said second photoconductive composition with respect to said red light; and a light filtering substance insensitive to said visible light and capable of absorbing light other than the red light, whereby said second photoconductive composition is rendered sensitive only to said red light; and

3. a third photoconductive composition comprising a photoconductor sensitive to the visible light; a sensitizing amount of a sensitizer capable of absorbing blue light for enhancing sensitivity of said third photoconductive composition with respect to said blue light; and a light filtering substance insensitive to said visible light and capable of absorbing light other than the blue light, whereby said third photoconductive composition is rendered sensitive only to said blue light.

11. The photoconductive element of claim 10, wherein the light filtering substance in each photoconductive composition is a dyestuff or pigment.

12. A photoconductive element according to claim 10 wherein amount of the light filtering substance added to each photoconductive composition is 5 30 parts by weight per parts by weight of the photoconductor.

13. A photoconductive element according to claim 12, wherein amount of said sensitizer added to each photoconductive composition is 0.003 l0 parts by weight per 100 parts by weight of the photoconductor.

14. The photoconductive element of claim 13, wherein the light filtering substance in each photoconductive composition is a dyestuff or pigment.

15. An electrophotographic recording material for making multicolored images comprising a mosaic-likedivided photoconductive film having at least one photoconductor, at least two sensitizer dyes, and at least two dyestuffs or pigments, wherein each individual section of the mosaic is sensitive to light of a limited region of the spectrum, each section of the mosaic containing a sensitizer dye sensitive to light in a broader region of the spectrum that in the corresponding limited region, said broader region including said corresponding limited region, and a dyestuff or pigment absorbing light in said broader region except for light in said corresponding limited region whereby undesired sensitizing of the photoconductor in each section of the mosaic by light outside of the corresponding limited region is prevented. 

1. A PHOTOCONDUCTOR MIXTURE SENSITIVE TO LIGHT OF A LIMITED REGION OF THE SPECTRUM COMPRISNG A PHOTOCONDUCTOR, AT LAST ONE SENSITIZER DYE SENSITIVE TO LIGHT IN A BROARDER REGION OF THE SPECTRUM THAN SAID LIMITED REGION, SAID BROADER REGION INCLUDING SAID LIMITING REGION, AND AT LEAST ONE DYESTUFF OR PIGMENT ABSORBING LIGHT IN SAID BROADER EXCEPT FOR LIGHT IN SAID LIMITING REGION WHEREBY UNDESIRED SENSITIZING OF SAID PHOTOCONDUCTOR BY LIGHT OUTSIDE SAID LIMITED REGION IS PREVENTED SAID MIXTURE CONTAINING 5 TO 30 PARTS BY WEIGHT OF SAID AT LAST ONE DYSTUFF OR PIGMENT AND 0.003 O 10 PARTS BY WEIGHT OF SAID AT LEAST ONE SENSITIZER DYE BASED ON 100 PARTS BY WEIGHT OF SAID PHOTOCONDUCTOR.
 2. A photoconductive material according to claim 1, wherein said sensitizer absorbs mainly green light and said light filtering substance is capable of absorbing light other than sAid green light.
 2. a second photoconductive composition comprising a photoconductor sensitive to the visible light; a sensitizing amount of a sensitizer capable of absorbing red light for enhancing sensitivity of said second photoconductive composition with respect to said red light; and a light filtering substance insensitive to said visible light and capable of absorbing light other than the red light, whereby said second photoconductive composition is rendered sensitive only to said red light; and
 3. a third photoconductive composition comprising a photoconductor sensitive to the visible light; a sensitizing amount of a sensitizer capable of absorbing blue light for enhancing sensitivity of said third photoconductive composition with respect to said blue light; and a light filtering substance insensitive to said visible light and capable of absorbing light other than the blue light, whereby said third photoconductive composition is rendered sensitive only to said blue light.
 3. A photoconductive material according to claim 2, wherein said mixture contains yellowish or orange dyestuff or pigment for filtering light having smaller wave lengths than green light and a green, blue or violet dye or pigment for filtering light having larger wave lengths than green light.
 4. A photoconductive material according to claim 1, wherein said sensitizer absorbs mainly red light and said light filtering substance is capable of absorbing light other than said red light.
 5. The photoconductive material of claim 4, wherein said mixture contains a red dye or pigment for filtering light having smaller wave lengths than red light.
 6. A photoconductive material according to claim 1, wherein said sensitizer absorbs mainly blue light and said light filtering substance is capable of absorbing light other than said blue light.
 7. A photoconductive material according to claim 6, wherein said mixture contains an orange dye or pigment for filtering light having larger wave lengths than blue light.
 8. A photoconductive material according to claim 1, wherein the photoconductor is selected from the group consisting of selenium, zinc oxide, titanium oxide and cadmium sulfide.
 9. A photoconductive material according to claim 1, wherein the photoconductor is an organic polymer selected from the group consisting of an aromatic and heterocyclic vinyl polymers.
 10. A photoconductive element comprising three kinds of homogeneous mixtures, each being regularly arranged in mosaic pattern on an electroconductive support, said homogeneous mixtures including the following three photoconductive compositions:
 11. The photoconductive element of claim 10, wherein the light filtering substance in each photoconductive composition is a dyestuff or pigment.
 12. A photoconductive element according to claim 10 wherein amount of the light filtering substance added to each photoconductive composition is 5 - 30 parts by weight per 100 parts by weight of the photoconductor.
 13. A photoconductive element according to claim 12, wherein amount of said sensitizer added to each photoconductive composition is 0.003 - 10 parts by weight per 100 parts by weight of the photoconductor.
 14. The photoconductive element of claim 13, wherein the light filtering substance in each photoconductive composition is a dyestuff or pigment.
 15. An electrophotographic recording material for making multicolored images comprising a mosaic-like-divided phoToconductive film having at least one photoconductor, at least two sensitizer dyes, and at least two dyestuffs or pigments, wherein each individual section of the mosaic is sensitive to light of a limited region of the spectrum, each section of the mosaic containing a sensitizer dye sensitive to light in a broader region of the spectrum than in the corresponding limited region, said broader region including said corresponding limited region, and a dyestuff or pigment absorbing light in said broader region except for light in said corresponding limited region whereby undesired sensitizing of the photoconductor in each section of the mosaic by light outside of the corresponding limited region is prevented. 